Wanted to have a font-size mixin that included the golden ratio, and music intervals. So here it is.

index.markdown

#headline ##healine 2

style.scss

@import "compass";
$root-font-size: 100% !default;

$root-font-multiplier:  ($root-font-size / ($root-font-size * 0 + 1))/100;

@mixin font-size($value, $increment, $ratio){
  @if $ratio == unison {
    $ratio: 1;  
  }

  @else if $ratio == minor-second {
    $ratio: 1.067;
  }
 
  @else if $ratio == major-second {
    $ratio: 1.125;
  }

  @else if $ratio == minor-third {
    $ratio: 1.2;
  }

  @else if $ratio == major-third {
    $ratio: 1.25;
  }

  @else if $ratio == perfect-fourth {
    $ratio: 1.333;
  }

  @else if $ratio == augmented-fourth {
    $ratio: 1.414;
  }

  @else if $ratio == diminished-fifth {
    $ratio: 1.414;
  }

 @else if $ratio == perfect-fifth {
    $ratio: 1.5;
  }

 @else if $ratio == minor-sixth {
    $ratio: 1.6;
  }

  @else if $ratio == major-sixth {
    $ratio: 1.667;
  }
  
   @else if $ratio == minor-seventh {
    $ratio: 1.778;
  }

  @else if $ratio == major-seventh {
          $ratio: 1.875;
  }

  @else if $ratio == octave {
          $ratio: 2;
  }

 @else if $ratio == major-tenth {
          $ratio: 2.5;
  }
 
 @else if $ratio == major-eleventh {
          $ratio: 2.667;
  }

   @else if $ratio == major-twelfth {
          $ratio: 3;
  }
 
  @else if $ratio == double-octave {
          $ratio: 4;
  }

  @else if $ratio == golden-ratio {
          $ratio: 1.618;
  }
  
  @else {
    $ratio: $ratio;
  }
  
  @if $increment > 0 {
      @for $i from 1 through $increment {
        $value: ($value * $ratio);
      }
    }
    @if $increment < 0 { 
      $increment: abs($increment);
        @for $i from 1 through $increment {
          $value: ($value / $ratio);
        }
    }   

  font-size: $value * $root-font-multiplier * 16px;
  font-size: $value * 1rem;
}

h1 {
  @include font-size(1, 4, diminished-fifth)
}

h2 {
  @include font-size(1.2, 3, perfect-fourth)
}